Changes in length of the radioulnar ligament and distal oblique bundle after Colles' fracture.

The purpose of this study was to investigate changes in length of the radioulnar ligament and distal oblique bundle (DOB) within the distal interosseous membrane after Colles' fracture and correlate the magnitude of the changes in length with clinical features. This study investigated 10 patients with malunion of a Colles' fracture. In three-dimensional computed tomography, the paths of the four limbs of the radioulnar ligament (superficial and deep, dorsal, and palmar limbs) and DOB were modelled and each path length was computed. Differences in length between the affected and contralateral unaffected side were calculated and correlated with the radiographic parameters of deformity on plain X-ray, subluxation of the DRUJ on CT, and limited range of forearm rotation in the clinical examination. In the malunited radius, the superficial and deep dorsal limbs of the radioulnar ligament were significantly elongated and DOB was significantly shortened compared with the contralateral side. These length changes correlated with radiographic radial shortening, subluxation of the DRUJ, and inversely correlated with limited range of forearm pronation. This study suggests that the dorsal radioulnar ligament would be overstretched and disrupted in Colles' fracture with severely increased radial shortening, producing laxity of the distal radioulnar joint that could negate limitation of pronation.